TW201935715A - Deep ultraviolet led and production method for same - Google Patents

Abstract

The invention is a deep ultraviolet LED, which is characterized in that it is a design wavelength set to λ, and has a reflective electrode layer (Au), a metal layer (Ni), and a p-type GaN contact layer in order from the opposite side from the sapphire substrate. , A P-Block layer formed of a p-type AlGaN layer, an i-guide layer formed of an AlN layer, a multiple quantum well layer, an n-type AlGaN contact layer, a u-type AlGaN layer, an AlN template, and the sapphire substrate described above, the P- The block layer has a film thickness of 52 nm to 56 nm, and is provided in a range from the interface of the metal layer and the p-type GaN contact layer in a thickness direction of the p-type GaN contact layer and does not exceed the p-type GaN contact. The reflective two-dimensional photonic crystal periodic structure with a plurality of holes is located at the interface between the layer and the P-Block layer. The holes are from the end surface of the sapphire substrate in the direction of the holes to the multiple quantum well layer and the above. The distance up to the interface of the i-guide layer satisfies λ / 2n _1Dneff in the vertical direction, and the distance ranges from 53 nm to 57 nm. The above-mentioned reflective two-dimensional photonic crystal periodic structure has a photon band gap opened relative to the TE polarized component. The above reflective two-dimensional photon Period periodic structure of the body with respect to light having a design wavelength of [lambda] satisfying the Bragg condition, and in Prague conditional equation mλ / _n 2Deff = 2a (wherein, m: number of times, λ: design _wavelength, n 2Deff: a two-dimensional photonic crystal The effective index of refraction, a: the period of the two-dimensional photonic crystal) m satisfies 2 ≦ m ≦ 4. When the radius of the above-mentioned void is set to R, the R / a ratio satisfies 0.30 ≦ R / a ≦ 0.40.

Description

Deep ultraviolet LED and manufacturing method thereof

The invention relates to an AlGaN-based deep ultraviolet LED (light-emitting diode) technology.

Deep UV LEDs with an emission wavelength of 200 nm to 355 nm are widely used in sterilization, water purification / air purification, and medical applications. They have attracted attention as alternative technologies for mercury lamp sterilization lamps. However, the power to light conversion efficiency (WPE) of LEDs is 2 to 3%, which is significantly lower than 20% of mercury lamps. The main reason is that the light extraction efficiency (LEE) is as low as 8% or less because the emitted light is absorbed by approximately 100% of the p-type GaN contact layer.

Patent Document 1 discloses that in a deep ultraviolet LED in which the film thickness of the p-type AlGaN layer is 100 nm or less, the position of the reflective photonic crystal structure close to the quantum well layer can increase the LEE by 2 to 3 times. In the case of the p-type AlGaN contact layer, about 23% of the LEE was obtained, and about 18% of the LEE was obtained in the pGaN contact layer. However, if the internal quantum efficiency is 50% and the voltage efficiency (electron injection efficiency × theoretical voltage / driving voltage) is 80%, the WPE is still estimated to be 7-9%.
[Prior technical literature]
[Patent Literature]

Patent Document 1: Japanese Patent No. 6156898

[Problems to be solved by the invention]

The power optical conversion efficiency (WPE) is as follows: ((internal quantum efficiency (IQE) × electron injection efficiency (EIE) × light extraction efficiency (LEE)) × ((theoretical voltage (Vt) / driving voltage (Vf))) In general, in order to exceed the WPE of the mercury lamp by 20%, it is required to suppress the driving voltage (Vf) as much as possible, and at the same time to increase the LEE compared to the value shown in Patent Document 1.

The invention is in a deep ultraviolet LED, and provides a new technology to further improve light extraction efficiency.
[Technical means to solve the problem]

According to a first aspect of the present invention, there is provided a deep ultraviolet LED, which is characterized in that the design wavelength is set to λ, and the reflective electrode layer (Au) and the metal layer (Ni) are sequentially provided from the opposite side from the sapphire substrate. , P-type GaN contact layer, P-Block layer formed from p-type AlGaN layer, i-guide layer formed from AlN layer, multiple quantum well layer, n-type AlGaN contact layer, u-type AlGaN layer, AlN template, and the above For the sapphire substrate, the film thickness of the P-Block layer is 52 nm to 56 nm, and it is provided in a range from the interface of the metal layer and the p-type GaN contact layer in the thickness direction of the p-type GaN contact layer without A reflective two-dimensional photonic crystal periodic structure with a plurality of holes that exceeds the position of the interface between the p-type GaN contact layer and the P-Block layer. The holes are from the end surface of the sapphire substrate in the direction of the holes to the above. The distance between the interface between the multiple quantum well layer and the i-guide layer satisfies λ / 2n _1Dneff in the vertical direction (where λ: design wavelength, n _1Dneff : layer structure from the end surface of the hole to the i-guide layer. Effective average refraction of each film thickness The distance ranges from 53 nm to 57 nm. The reflective two-dimensional photonic crystal periodic structure has a photon band gap opened with respect to the TE polarized component. The period a of the reflective two-dimensional photonic crystal periodic structure is relative to the above. The light at the design wavelength λ satisfies the condition of Bragg and is in Bragg's conditional expression mλ / n _2Deff = 2a (where m: order, λ: design wavelength, n _2Deff : effective refractive index of a two-dimensional photonic crystal, a: two-dimensional The number of times m of the period of the photonic crystal) satisfies 2 ≦ m ≦ 4. When the radius of the above-mentioned hole is set to R, the R / a ratio satisfies 0.30 ≦ R / a ≦ 0.40.

As for the method for measuring the parameters of the above-mentioned deep ultraviolet LED, the thickness of each layer formed by epitaxial growth can be measured using an optical interference film thickness measuring device. Furthermore, when the thickness of each layer is sufficiently different in the composition of adjacent layers (for example, when the Al composition ratio is different from 0.01 or more), the cross-section observation of the growth layer using a transmission electron microscope can be performed. To figure it out. In addition, when the thickness of each layer is thin, such as a multiple quantum well or a superlattice structure, TEM-EDS (Transmission Electron Microscopy-energy dispersed X-ray spectroscopy) can be used. Transmission electron microscope-energy dispersive X-ray analysis ) To measure the thickness. The periodic structure or shape of the photonic crystal and the measurement of the distance between the quantum well layer and the photonic crystal can be observed by using the scanning electron microscope (STEM) Scanning Transmission Electron Microscopy (High-Angle Annular) mode. Dark Field).

According to a second aspect of the present invention, there is provided a deep ultraviolet LED, which is characterized in that the design wavelength is set to λ, and the reflective electrode layer (Au) and the metal layer (Ni) are sequentially provided from the opposite side from the sapphire substrate. , P-type AlGaN contact layer transparent to wavelength λ, P-Block layer formed of p-type AlGaN layer, i-guide layer formed of AlN layer, multiple quantum well layer, n-type AlGaN contact layer, u-type AlGaN layer , AlN template, and the sapphire substrate, the film thickness of the P-Block layer is 44 nm to 48 nm, and the thickness is provided from the interface of the metal layer and the p-type AlGaN contact layer to the thickness of the p-type AlGaN contact layer. Periodic structure of a reflective two-dimensional photonic crystal with a plurality of voids within the range of the direction and not exceeding the position of the interface between the p-type AlGaN contact layer and the P-Block layer, the voids are the sapphire from the voids The distance from the end surface in the substrate direction to the interface between the multiple quantum well layer and the i-guide layer satisfies λ / 2n _1Dneff (where λ: design wavelength, n _1Dneff : from the end surface of the hole to the i- layered structure up to the guide layer Effective average refractive index of each film thickness), the distance ranges from 53 nm to 61 nm. The above-mentioned reflective two-dimensional photonic crystal periodic structure has a photon band gap opened relative to the TE polarized component. The above-mentioned reflective two-dimensional photon The period a of the crystal periodic structure satisfies the Bragg condition with respect to the light of the design wavelength λ described above, and is in Bragg's conditional expression mλ / n _2Deff = 2a (where m: the number of times, λ: the design wavelength, and n _2Deff : the two-dimensional photonic crystal The effective index of refraction, a: the period of the two-dimensional photonic crystal) m satisfies 1 ≦ m ≦ 4, and when the radius of the above-mentioned hole is set to R, the R / a ratio satisfies 0.20 ≦ R / a ≦ 0.40.

As for the method for measuring the parameters of the above-mentioned deep ultraviolet LED, the thickness of each layer formed by epitaxial growth can be measured using an optical interference film thickness measuring device. Furthermore, when the thickness of each layer is sufficiently different in the composition of adjacent layers (for example, when the Al composition ratio is different from 0.01 or more), the cross-section observation of the growth layer using a transmission electron microscope can be performed. To figure it out. When the thickness of each layer is thin, such as a multiple quantum well or a superlattice structure, TEM-EDS can be used to measure the thickness. The photonic crystal's periodic structure or shape and the distance between the quantum well layer and the photonic crystal can be measured by observing a HAADF (high-angle scattering annular dark field) image using a transmission electron microscope (STEM) mode. Figure it out.

According to a third aspect of the present invention, there is provided a deep ultraviolet LED, which is characterized in that the design wavelength is set to λ, and it has a reflective electrode layer (Rh) in order from the side opposite to the sapphire substrate, and is transparent to the wavelength λ. P-type AlGaN contact layer, P-Block layer formed from p-type AlGaN layer, i-guide layer formed from AlN layer, multiple quantum well layer, n-type AlGaN contact layer, u-type AlGaN layer, AlN template, and the above The sapphire substrate has a film thickness of 44 nm to 48 nm for the P-Block layer, and is provided in a range from the interface between the reflective electrode layer and the p-type AlGaN contact layer in a thickness direction of the p-type AlGaN contact layer and Periodic structure of a reflective two-dimensional photonic crystal with a plurality of holes that does not exceed the position of the interface between the p-type AlGaN contact layer and the P-Block layer. The holes are from the end surface of the holes to the direction of the sapphire substrate to The distance between the interface between the multiple quantum well layer and the i-guide layer satisfies λ / 2n _1Dneff in a vertical direction (where λ: design wavelength, n _1Dneff : a layer from the end surface of the hole to the i-guide layer Structure of each film Thick effective average refractive index), the distance ranges from 53 nm to 61 nm. The above-mentioned reflective two-dimensional photonic crystal periodic structure has a photon band gap opened relative to the TE polarized component. The light of the period a with respect to the above-mentioned design wavelength λ satisfies the condition of Bragg, and is in Bragg's conditional expression mλ / n _2Deff = 2a (where m: degree, λ: design wavelength, n _2Deff : effective refractive index of the two-dimensional photonic crystal , A: The period m of the two-dimensional photonic crystal) The number m satisfies 1 ≦ m ≦ 4. When the radius of the hole is set to R, the R / a ratio satisfies 0.20 ≦ R / a ≦ 0.40. As for the method for measuring the parameters of the above-mentioned deep ultraviolet LED, the thickness of each layer formed by epitaxial growth can be measured using an optical interference film thickness measuring device. Furthermore, when the thickness of each layer is sufficiently different in the composition of adjacent layers (for example, when the Al composition ratio is different from 0.01 or more), the cross-section observation of the growth layer using a transmission electron microscope can be performed. To figure it out. When the thickness of each layer is thin, such as a multiple quantum well or a superlattice structure, TEM-EDS can be used to measure the thickness. The photonic crystal's periodic structure or shape and the distance between the quantum well layer and the photonic crystal can be measured by observing a HAADF (high-angle scattering annular dark field) image using a transmission electron microscope (STEM) mode. Figure it out.

According to a fourth aspect of the present invention, a method for manufacturing a deep ultraviolet LED is provided, which is a method for manufacturing a deep ultraviolet LED with a design wavelength set to λ, and has the following steps: forming a multilayer structure with a sapphire substrate as a growth substrate A step of forming a P-Block layer including a reflective electrode layer, a metal layer, a p-type GaN contact layer, a p-type AlGaN layer transparent to a wavelength λ, and AlN from the opposite side of the sapphire substrate. In the step of forming a multilayer structure including an i-guide layer, a multiple quantum well layer, an n-type AlGaN contact layer, a u-type AlGaN layer, and an AlN template, the film thickness of the P-Block layer is 52 nm to 56 nm. Crystal growth is performed; and formed in a range from the interface between the metal layer and the p-type GaN contact layer in the thickness direction of the p-type GaN contact layer and not exceeding the thickness of the p-type GaN contact layer and the P-Block layer The step of forming a reflective two-dimensional photonic crystal with a plurality of voids at the interface; a step of forming the voids from the end surface of the sapphire substrate in the direction of the voids to the multiple quantum well layer and the ig a step at a distance of 53 nm to 57 nm up to the interface of the uide layer; a step of preparing a mold for forming the reflective two-dimensional photonic crystal periodic structure; forming a resist layer on the p-type GaN contact layer And a step of transferring the structure of the mold by a nano-imprint method; a step of forming the two-dimensional photonic crystal periodic structure by etching the p-type GaN contact layer using the resist layer as a mask; and forming the reflective type 2 A step of forming a two-dimensional photonic crystal structure, and forming the above-mentioned metal layer and the reflective electrode layer by oblique evaporation in this order; and a step of forming a reflective electrode layer on the above-mentioned metal layer.

In the method for measuring the parameters in the above-mentioned manufacturing method of the deep ultraviolet LED, the entire thickness of each layer formed by epitaxial growth can be measured using an optical interference film thickness measuring device. Furthermore, when the thickness of each layer is sufficiently different in the composition of adjacent layers (for example, when the Al composition ratio is different from 0.01 or more), the cross-section observation of the growth layer using a transmission electron microscope can be performed. To figure it out. When the thickness of each layer is thin, such as a multiple quantum well or a superlattice structure, TEM-EDS can be used to measure the thickness. The photonic crystal's periodic structure or shape and the distance between the quantum well layer and the photonic crystal can be measured by observing a HAADF (high-angle scattering annular dark field) image using a transmission electron microscope (STEM) mode. Figure it out.

According to a fifth aspect of the present invention, a method for manufacturing a deep ultraviolet LED is provided, which is a method for manufacturing a deep ultraviolet LED with a design wavelength set to λ, and has the following steps: preparing a laminated structure with a sapphire substrate as a growth substrate In the step, the laminated structure system includes a reflective electrode layer, a metal layer, a p-type AlGaN contact layer transparent to a wavelength λ, a P-Block layer formed of a p-type AlGaN layer, and the like from the opposite side to the sapphire substrate. In the step of forming an i-guide layer, a multiple quantum well layer, an n-type AlGaN contact layer, a u-type AlGaN layer, and an AlN template laminated structure formed of an AlN layer, the film thickness of the P-Block layer is 44 nm to Crystal growth was performed at 48 nm; formed in a range from the interface of the metal layer and the p-type AlGaN contact layer in the thickness direction of the p-type AlGaN contact layer and not exceeding the p-type AlGaN contact layer and the P-Block The step of forming a periodic two-dimensional photonic crystal structure with a plurality of holes at the interface of the layer, the holes are formed from the end surface of the growth substrate in the direction of the holes to the multiple quantum wells. A step with a distance of 53 nm to 61 nm from the interface with the i-guide layer; a step of preparing a mold for forming the reflective two-dimensional photonic crystal periodic structure; forming on the p-type AlGaN contact layer A step of forming a resist layer and transferring the structure of the mold by a nano-imprint method; a step of etching the p-type AlGaN contact layer using the resist layer as a mask to form a two-dimensional photonic crystal periodic structure; forming A step of forming the reflective two-dimensional photonic crystal structure, and forming the metal layer by an oblique evaporation method; and a step of forming a reflective electrode layer from Au on the metal layer.

In the method for measuring the parameters in the above-mentioned manufacturing method of the deep ultraviolet LED, the entire thickness of each layer formed by epitaxial growth can be measured using an optical interference film thickness measuring device. Furthermore, when the thickness of each layer is sufficiently different in the composition of adjacent layers (for example, when the Al composition ratio is different from 0.01 or more), the cross-section observation of the growth layer using a transmission electron microscope can be performed. To figure it out. When the thickness of each layer is thin, such as a multiple quantum well or a superlattice structure, TEM-EDS can be used to measure the thickness. The photonic crystal's periodic structure or shape and the distance between the quantum well layer and the photonic crystal can be measured by observing a HAADF (high-angle scattering annular dark field) image using a transmission electron microscope (STEM) mode. Figure it out.

According to a sixth aspect of the present invention, a method for manufacturing a deep ultraviolet LED is provided, which is a method for manufacturing a deep ultraviolet LED with a design wavelength set to λ, and has the following steps: forming a multilayer structure with a sapphire substrate as a growth substrate In the step, the above-mentioned laminated structure system is formed from a p-type AlGaN contact layer, which includes a reflective electrode layer, is transparent to the wavelength λ, a P-Block layer formed of a p-type AlGaN layer, and an AlN layer. In the step of forming the laminated structure of the i-guide layer, the multiple quantum well layer, the n-type AlGaN contact layer, the u-type AlGaN layer, and the AlN template, the film thickness of the P-Block layer is 44 nm to 48 nm. Crystal growth; formed in a range from the interface of the metal layer and the p-type AlGaN contact layer in the thickness direction of the p-type AlGaN contact layer and not exceeding the interface of the p-type AlGaN contact layer and the P-Block layer The step of forming a reflective two-dimensional photonic crystal with a plurality of voids at a periodic structure; forming the voids from the end surface of the growth substrate in the direction of the voids to the multiple quantum well layer and the i -The step of the distance from the interface of the -guide layer is 53 nm to 61 nm; the step of preparing a mold for forming the reflective two-dimensional photonic crystal periodic structure; forming a resist on the p-type AlGaN contact layer A step of transferring the structure of the mold using a nano-imprint method; forming a two-dimensional photonic crystal periodic structure by etching the p-type AlGaN contact layer using the resist layer as a mask; and forming the reflection A two-dimensional photonic crystal structure, and the step of forming the above-mentioned reflective electrode layer by Rh by an oblique vapor deposition method.

In the method for measuring the parameters in the above-mentioned manufacturing method of the deep ultraviolet LED, the entire thickness of each layer formed by epitaxial growth can be measured using an optical interference film thickness measuring device. Furthermore, when the thickness of each layer is sufficiently different in the composition of adjacent layers (for example, when the Al composition ratio is different from 0.01 or more), the cross-section observation of the growth layer using a transmission electron microscope can be performed. To figure it out. When the thickness of each layer is thin, such as a multiple quantum well or a superlattice structure, TEM-EDS can be used to measure the thickness. The photonic crystal's periodic structure or shape and the distance between the quantum well layer and the photonic crystal can be measured by observing a HAADF (high-angle scattering annular dark field) image using a transmission electron microscope (STEM) mode. Figure it out.

This specification contains the disclosure of Japanese Patent Application No. 2018-012073, which is the basis of the priority of this application.
[Effect of the invention]

According to the present invention, the synergy between the vertical Bragg reflection and the reflective two-dimensional photonic crystal can dramatically improve the LEE and even WPE of deep ultraviolet LEDs.

Hereinafter, the deep ultraviolet LED according to the embodiment of the present invention will be described in detail with reference to the drawings.

(First Embodiment)
As a deep ultraviolet LED according to the first embodiment of the present invention, the structure (cross-sectional view and top view) of an AlGaN deep ultraviolet LED with a design wavelength λ of 275 nm is shown in FIGS. 1A (a-1) and (a-2).
Specifically, the sapphire substrate 1, the AlN template 2, the u-type AlGaN layer 3, the n-type AlGaN contact layer 4, the multiple quantum well layer 5 (among which multiple quantum The well layer 5 series quantum well layer is composed of 3 layers (51, 53, 55), and the structure of the barrier layer (52, 54) is spaced between each quantum well layer, i-guide layer 6 (among which, i-guide layer 6 is formed from an AlN layer), P-Block layer 7 (where P-Block layer 7 is formed from an AlGaN layer), p-type GaN contact layer 8, metal layer 9 (where metal layer 9 is formed from a Ni layer), a reflective electrode Layer 10 (where the reflective electrode layer is formed of Au). The film thickness of the P-Block layer 7 is 52 nm to 56 nm. In addition, a reflective two-dimensional photonic crystal period structure 100 is provided within a range of the thickness direction of the p-type GaN contact layer 8 and at a position not exceeding the interface between the p-type GaN contact layer 8 and the P-Block layer 7, and the photonic crystal period Structure 100 has pores (column structure, pores) 101 (h). The pores 101 are provided at a distance G from the end surface in the direction of the sapphire substrate 1 to the interface between the multiple quantum well layer 5 and the i-guide layer 6 is 53 nm. At a position of ~ 57 nm, the distance G satisfies the Bragg reflection conditions in the vertical direction. The entire thickness of each layer formed by epitaxial growth can be measured using an optical interference film thickness measuring device. Furthermore, when the thicknesses of the layers are sufficiently different in the composition of adjacent layers (for example, when the Al composition ratio is different from 0.01 or more), the cross-section of a growth layer using a transmission electron microscope may be used. Observe to calculate. When the thickness of each layer is thin, such as a multiple quantum well or a superlattice structure, TEM-EDS can be used to measure the thickness. The photonic crystal's periodic structure or shape and the distance between the quantum well layer and the photonic crystal can be measured by observing a HAADF (high-angle scattering annular dark field) image using a transmission electron microscope (STEM) mode Figure it out.

FIG. 2 shows the relationship between the cumulative film thickness and the refractive index difference in the multilayer structure from the multiple quantum well layer 5 to the p-type GaN contact layer 8 related to the Bragg reflection in the vertical direction.

According to the expression of Bragg scattering conditions (mλ / n _1Deff = 2a, m: degree, n _1Deff : effective refractive index of each film thickness of the laminated structure from the end face of the hole 101 (h) to the i-guide layer 6, λ : Design wavelength, a: period), calculate the distance G (period) to obtain the effect of Bragg reflection in the vertical direction and the film thickness of the P-Block layer 7.

The respective refractive indices (n) of the i-guide layer 6 and the P-Block layer 7 at the design wavelength of 275 nm are i-guide layer 6 (n ₁ = 2.300), and P-Block layer 7 (n ₂ = 2.594). The effective refractive index n _1Deff is obtained using the _formula n _1Deff = [n ₂ ² + (n ₁ ² -n ₂ ² ) (d / a) ² ] ^0.5 . When the film thickness of the i-guide layer 6 is d, for example, 1 nm, the value of d / a is 0.019, so n _{1Deff is} 2.589. If it is set to m = 1, and these are substituted into the above expression of the Bragg scattering condition, the period a can be derived to be 53 nm. Here, since the film thickness of the i-guide layer 6 is 1 nm, the film thickness of the P-Block layer 7 is 52 nm. That is, the film thickness of the P-Block layer 7 which can obtain a reflection effect in the vertical direction is 52 nm here.

Table 1 shows the results of FDTD simulation analysis related to the Bragg reflection effect in the vertical direction.

[Table 1]
[Note]
-G53 nm: Set the monitor at a position 53 nm away from the interface between the quantum well layer 55 and the i-guide layer 6 toward the sapphire substrate.
+ G53 nm: Set the monitor at a position 53 nm away from the interface between the quantum well layer 55 and the i-guide layer 6 toward the p-type GaN contact layer. Output ratio: P-Block film thickness 52 nm / 40 nm

Table 1 shows the situation where the P-Block layer has a film thickness of 40 nm and 52 nm, and the monitor is set at a distance of 53 nm from the interface between the quantum well layer 55 and the i-guide layer 6 in the direction of the sapphire substrate 1. (Table 1 "-G53 nm"), and a case where it is placed at a distance of 53 nm from the interface between the quantum well layer 55 and the i-guide layer 6 in the direction of the p-type GaN contact layer 8 (Table 1 "+ G53 nm ″) and the output ratio of the P-Block layer film thickness to 52 nm and the film thickness to 40 nm.

According to Table 1, in the monitor ("-G53 nm") above the quantum well layer, the output of the P-Block layer with a film thickness of 52 nm is 1.8 times the film thickness of 40 nm, but the monitoring on the lower side is Device ("+ G53 nm") to obtain an output ratio of 2.6 times that is different from that. The reason is that in the lower side ("+ G53 nm"), the distance of 53 nm when the P-Blcok layer is 40 nm is the position where it enters the absorption region of the p-type GaN contact layer, so the P-Block film is 40 nm The output is greatly reduced.

From these results, it can be confirmed that if the distance G to obtain the Bragg reflection effect in the vertical direction is 53 nm and the P-Blcok layer is 52 nm, the reflection effect is obtained without entering the absorption region of the p-type GaN contact layer.

Second, the reflective two-dimensional photonic crystal periodic structure 100 is shown in the xy plan view in FIG. 1A (a-2), and has a hole 101 (h) with a circle of radius R as a cross section. The layer 8 is formed of small air or the like, and is formed into a columnar structure (hole structure) in a triangular lattice shape at a period a along the x direction and the y direction. In addition, in order to prevent damage to the P-Block layer 7 caused by dry etching, the hole 101 (h) is a structure that does not reach the interface between the p-type GaN contact layer 8 and the P-Block layer 7 and is provided in the hole. The distance (G) between the end surface of the sapphire substrate 1 in 101 (h) and the quantum well layer 55 is in a range of 53 nm to 57 nm.

In the reflective two-dimensional photonic crystal periodic structure 100, deep-ultraviolet light TE light and TM light of a wavelength λ emitted by the multiple quantum well layer 5 are radiated in all directions and propagate through the medium in an elliptical polarization.

The reflective two-dimensional photonic crystal periodic structure 100 disposed in the p-type GaN contact layer 8 at a distance of G53 nm to 57 nm from the quantum well layer 55 is formed as a p-type GaN contact layer 8 having different refractive indices and air. Two constructs. When the ratio R / a ratio of the radius R to the period a of the hole 101 (h) is set to, for example, 0.40, the filling factor f of the photonic crystal 100 is expressed by the formula f = 2π / 3 ^0.5 × (R / a) ² When calculated, f = 0.58. Furthermore, the effective refractive index n _2Deff is calculated from the refractive index n3 of the air n3 = 1.0, the refractive index n _{4 of the} p-type GaN contact layer 8 = 2.631, and f = 0.58 to obtain n _2Deff = (n ₄ ² + (n ₃ ² -n ₄ ² ) × f) ^0.5 = 1.867.

Furthermore, the wavelength range of deep ultraviolet (DUV) light is 200 nm to 355 nm, and the refractive index n and the extinction coefficient k are different depending on the wavelength. Therefore, if the selected wavelength λ changes, the calculation parameters of the above photonic crystal also change, so the film thickness of the P-Block layer and the distance between the quantum well layer and the two-dimensional photonic crystal will also change. In addition, the refractive index and extinction coefficient used in this calculation are literature values, but these values vary slightly according to their film thickness. Therefore, the film thickness of the P-Block layer and the quantum well layer and the two-dimensional photonic crystal are different. The distance will also change.

Moreover, when the emission wavelength λ = 275 nm, the reflective two-dimensional photonic crystal periodic structure 100 satisfies the Bragg scattering condition (mλ / n _2Deff = 2a, where n _{2Deff is} the effective refractive index of the two-dimensional photonic crystal, a: 2D The photon band structure of TM light and TE light in the case of the period of PhC, m: the number of times) is obtained by the plane wave expansion method. 3A (a-1) and (a-2) show respective photon band structure diagrams of TM light and TE light when R / a = 0.40.

Similarly, the respective photon band structures of TM light and TE light when R / a = 0.30 are shown in FIG. 3B (b-1) and (b-2), and when R / a = 0.20 The photon band structures of TM light and TE light are shown in Figs. 3C (c-1) and (c-2).

In two-dimensional reflective photonic crystals, as shown in Figs. 3A (a-1), 3B (b-1), and 3C (c-1), TM light does not observe a photon band gap (PBG), but In TE light, PBG is observed between the first photon band (ω1TE) and the second photon band (ω2TE) as shown in FIGS. 3A (a-2), 3B (b-2), and 3C (c-2). Moreover, as shown in FIGS. 3A (a-2), 3B (b-2), and 3C (c-2), the size of PBG in TE light is the largest at R / a = 0.40, and as R / a changes Large, PBG also becomes large.

In addition, if the film thickness of the P-Block layer 7 becomes thick, the driving voltage (Vf) becomes higher. For example, at a wavelength of 275 nm and a P-Block layer film thickness of 40 nm, Vf is about 6 V, but if the P-Block layer film thickness increases by 10 nm, Vf increases by 1 V. Therefore, in order to suppress Vf, it is necessary to make the film thickness of the P-Block layer as thin as possible. However, since the light extraction efficiency is greatly improved by the synergistic effect of the vertical Bragg reflection and the reflective two-dimensional photonic crystal, it is important to optimize the film thickness of the P-Block layer. Therefore, in this embodiment, by using FDTD method and ray tracing method, the synergistic effect of obtaining the above-mentioned Bragg reflection and reflection type two-dimensional photonic crystal in the vertical direction is obtained, and the LEE is obviously improved, and Vf and Appropriate conditions for selecting the film thickness of the P-Block layer, that is, the parameters of the distance between the quantum well layer 55 and the reflective two-dimensional photonic crystal structure, the thickness of the P-Block layer film, and the periodic structure of the two-dimensional photonic crystal The number m of the scattering conditions mλ / n _2Deff = 2a and the periods a and R / a).

Table 2 shows the calculation model of the deep ultraviolet LED structure of the FDTD method, and Table 3 shows the parameters of the calculation model of the reflective two-dimensional photonic crystal structure.

[Table 2]

[table 3]

FIG. 4 is a cross-sectional view near a photonic crystal periodic structure in a deep ultraviolet LED structure having a film thickness of 40 nm as an example of a calculation model of the FDTD method. The structure of the calculation model makes the film thickness of the P-Block layer in the range of 40 nm to 60 nm variable in units of 4 nm. When using the non-reflective two-dimensional photonic crystal periodic structure (2D-PhC), there are reflections. In the case of a two-dimensional photonic crystal periodic structure (2D-PhC), the comparison is analyzed. The formation position of 2D-PhC is set from the interface between the P-Block layer and the p-type GaN contact layer to the interface between the metal layer (Ni) and the p-type GaN contact layer as shown in FIG. 4.

The simulation analysis results of the above calculation model are shown in FIG. 5 and FIG. 6. Fig. 5 shows that the P-Block layer is made variable in units of 4 nm in the range of a film thickness of 40 nm to 60 nm, and 2D-PhC is 2D-PhC when the number of times m = 4 and R / a = 0.40. In the case and the case without 2D-PhC, the respective output (w) changes. As shown in FIG. 5, in the case of 2D-PhC and without 2D-PhC, the film thickness of the P-Block layer is 52 nm to 56 nm, and the output greatly increases.

Also, according to FIG. 5, in a structure without 2D-PhC, the output when the P-Block layer film thickness is 52 nm to 56 nm is compared with the case where the P-Block layer film thickness is 40 nm. About 2 times. This phenomenon indicates that the laminated structure of the i-guide layer and the P-Block layer in the present structure obtains a vertical Bragg reflection effect when the film thickness of the P-Block layer is 52 nm to 56 nm.

In addition, FIG. 6 is a graph showing the increase ratio of the LEE when the structure with 2D-PhC is compared with the structure without 2D-PhC. As shown in Figure 6, it shows that the LEE increases approximately 2.6 times when the film thickness is 52 nm, and the LEE increases approximately 2.3 times when the film thickness is 56 nm. It can be said that when the film thickness of the P-Block layer is 52 nm to 56 nm, verticality is obtained. Coordinated effect of directional Bragg reflection and reflective two-dimensional photonic crystal.

The design of the reflective two-dimensional photonic crystal (2D-PhC) is in the 2D-PhC plane, according to the formula of Bragg scattering conditions mλ / n _2Deff = 2asinθ (where m: the number of times, n _2Deff : the 2D-PhC periodic structure Effective refractive index, λ: design wavelength, a: period of 2D-PhC). FIG. 7 is a graph showing the state densities of respective photons of R / a = 0.20 and R / a = 0.40 in 2D-PhC. The reflection intensity of a photonic crystal is related to the state density of the photon. As shown in FIG. 7, the larger the R / a, the greater the change in the state density of the photon. Furthermore, DUV light incident on 2D-PhC formed near the quantum well layer (light emitting layer) generates a standing wave in the 2D-PhC plane. Moreover, when the distance between the quantum well layer and 2D-PhC satisfies λ / 2n _1Deff , the DUV light incident into the 2D-PhC plane generates Bragg reflection in the vertical direction and reflects in the direction of the sapphire substrate. (See Figure 8).

It is considered that in the structure of the deep ultraviolet LED in this embodiment, when the distance between the quantum well layer and the 2D-PhC is 53 nm, the Bragg reflector is best satisfied in the vertical direction, so a larger reflection effect is obtained.

FIG. 9 shows the time-dependent change in the electric field strength from the quantum well layer to the vicinity of the p-type GaN contact layer when the distance between the quantum well layer and 2D-PhC is set to 53 nm as the analysis result of the FDTD method to verify these. FIG. 9 shows the cross section when there is no 2D-PhC and the case where there is 2D-PhC, and the electric field strength in the 2D-PhC plane. It can be seen that Fig. 9 (a) is a cross section of a structure without 2D-PhC, and the electric field spreads uniformly in all directions. In contrast, when there is a 2D-PhC in Fig. 9 (b), the electric field does not invade into 2D-PhC and Be reflected. In addition, if the electric field distribution in the 2D-PhC plane is observed, it can be confirmed that a standing wave appears in Fig. 9 (d) with a 2D-PhC structure compared with Fig. 9 (c) without a 2D-PhC structure.

According to the foregoing, the optimal value of the distance (G) between the quantum well layer and the 2D-PhC to obtain the synergistic effect of 1D-PhC and 2D-PhC was obtained through simulation analysis.

First, confirm the output of the P-Block layer with a thickness of 40 nm, 48 nm, and 52 nm due to the difference in the distance G between the quantum well layer and 2D-PhC. The distance G between the quantum well layer and 2D-PhC is set to be variable in units of 4 nm between 1 nm and 57 nm. The 2D-PhC is R / a = 0.30 and R / a = 0.40, and the number of times m is set. m = 4. The analysis results of the FDTD method are shown in FIG. 10.

As shown in Figure 10, in the comparison of the film thickness of the P-Block layer, the difference between the film thickness of 40 nm and the film thickness of 48 nm is the distance between the maximum output G49 nm, the P-Block film thickness of 48 nm and the film thickness of 40 nm. Than about 1.2 times. On the other hand, it was confirmed that the output of the P-Block film with a film thickness of 52 nm became the maximum at a distance of G53 nm. At this time, the output was doubled with respect to the film thickness of 48 nm.

In addition, FIG. 11 shows the increase rate of LEE under the same simulation conditions as in FIG. 10 when compared with the case where the structure has 2D-PhC without the structure with 2D-PhC. According to FIG. 11, at a film thickness of 52 nm, and a distance of G53, the LEE increases by 2.6 times in a structure with 2D-PhC. As a result, the distance G between the quantum well layer and 2D-PhC coincided with 53 nm, which is the distance that satisfies the above-mentioned Bragg condition in the vertical direction. That is to say, the P-Block layer with a maximum period of 53 nm that meets the maximum Bragg reflection effect in the vertical direction and a film thickness of 52 nm satisfies both the output and the LEE increase rate. The best conditions for synergy.

Furthermore, in FIG. 10, the distance G49 output at the same thickness as the P-Block film thickness of 52 nm is about the same as the distance G53. In the distance G49, the void of the reflective two-dimensional photonic crystal structure exceeds the p-type GaN contact layer. It is etched until it penetrates into the P-Block layer, and there is a possibility of causing etching damage to the P-Block layer, so it cannot be selected. In the case of the distance G57, it indicates that the output is lower than the distance G53, but the output is relatively large. Therefore, the distance G between the quantum well layer and the reflective two-dimensional PhC is selected from 53 nm to 57 nm.

In addition, regarding the distance G for the synergistic effect of the quantum well layer and the reflective two-dimensional photonic crystal, a maximum of 57 nm is also selected. Therefore, if the film thickness of the i-guide layer is 1 nm, the film thickness of the P-Block layer is appropriately 52. nm to 56 nm. Therefore, when the film thickness of the P-Block layer is 52 nm and 56 nm, the FDTD analysis is performed from the viewpoint of the R / a dependency and the number-dependence of 2D-PhC. In addition, since this analysis was compared with a standard LED structure, when the standard P-Block layer film thickness was 40 nm, comparison was made with a structure without 2D-PhC. Regarding the R / a dependency, the number of times is m = 4, and R / a = 0.20 to 0.40 is variable. Regarding the number of times dependency, R / a is set to R / a = 0.40, and is variable from m = 1 to 4. As a result of these, the comparison of the LEE increase magnification and the output value is shown in FIGS. 12 and 13.

Regarding the R / a dependency, FIG. 12 (a) shows the increase rate of LEE, and FIG. 12 (b) shows the output value. Regarding the frequency dependence, FIG. 13 (a) shows the LEE increase magnification, and FIG. 13 (b) shows the output value. As shown in Fig. 12 (a), (b), Fig. 13 (a), (b), it can be confirmed that in any of the results, when the P-Block film thickness is 52 nm and 56 nm, the same results are obtained. The degree of output and LEE increase rate. Furthermore, based on the analysis results, it can be confirmed that, as the optimal parameter of 2D-PhC, R / a = 0.30 or R / a = 0.40 is preferred, and the number of times is preferably m = 3 or m = 4.

Furthermore, the conditions of appropriate R / a and the number of times for 2D-PhC are also expressed by simulation analysis using the FDTD method. According to FIG. 11 and FIG. 12, in a comparison between R / a = 0.30 and R / a = 0.40, R / a = 0.40 (see FIG. 7) with a large change in the state density of the photon is shown in the film thickness of the P-Block layer 40 The reflection effect is higher among any of nm, 48 nm, and 52 nm. Therefore, the distance G between the quantum well layer and 2D-PhC was fixed to G53 nm, which is the distance that satisfies the above-mentioned Bragg condition in the vertical direction, and the order dependency of R / a = 0.40 was confirmed (FIG. 15). At the same time, the R / a dependency of the number of times m = 4 was also confirmed (FIG. 14). In addition, this analysis is also compared with a standard LED structure. Therefore, when the standard P-Block layer film thickness is 40 nm, a comparison with a structure without 2D-PhC is performed.

FIG. 14 (a) shows the increase in LEE in each R / a when the number of times is set to m = 4 at G53 nm, R / a is set to R / a = 0.20, R / a = 0.30, and R / a = 0.40. The R / a dependency of the magnification, and FIG. 14 (b) shows the R / a dependency of the output value. As shown in FIG. 14 (a), it can be confirmed that the "pGaN_Pblock52 nm_m4" has about 2.5 times the LEE when R / a = 0.20, but more than 5 times when R / a = 0.40. It can also be seen in FIG. 14 (b) that as R / a becomes larger, the output becomes larger.

Fig. 15 (a) shows the dependence of the number of times on the increase rate of LEE in each of the times when R / a = 0.40 is set at G53 nm, and the times are set to m = 1 ~ 4. Fig. 15 (b) also shows the output Value-dependent. According to FIG. 15 (a), the “pGaN_Pblock52 nm_R / a0.40” has an increase rate of LEE of about 3 to 4 times in the number of times m = 1 to 2, but about 5 to 6 times in the number of times m = 3 to 4. It can also be confirmed in FIG. 15 (b) that the number of times m = 3 to 4 is compared with the number of times m = 1 to 2 to obtain a larger output.

For such verification, the LEE value was obtained and confirmed by cross-simulation with the ray tracing method. Figure 16 shows the calculation model and analysis results of the ray tracing method. In the normal tracking method, since the nano-scale calculation cannot be performed, firstly, the present embodiment is calculated by cross simulation of multiplying the LEE value calculated by the ray tracing method with the LEE increase factor derived by the FDTD method. The LEE value of the LED structure. Table 4 shows the results.

[Table 4]

As shown in Table 4, the film thickness of the P-Block layer is 52 nm, the distance between the quantum well layer and 2D-PhC is G53 nm, R / a = 0.40, and the number of times m = 3 is 27.5%, which is the same as the number of times m = 4. Indicates a LEE value of 25.5%. According to this embodiment, the LEE can be further improved.

(Second Embodiment)
As a deep ultraviolet LED according to the second embodiment of the present invention, the structure (cross-sectional view and top view) of an AlGaN deep ultraviolet LED with a design wavelength λ of 275 nm is shown in FIGS. 1B (b-1) and (b-2).
Specifically, the sapphire substrate 1, AlN template 2, u-type AlGaN layer 3, n-type AlGaN contact layer 4, multiple quantum well layer 5 (among which multiple quantum The well layer 5 is a quantum well layer composed of 3 layers (51, 53, 55) with a barrier layer (52, 54) structure between each quantum well layer), i-guide layer 6 (among which, i-guide layer 6 is formed from an AlN layer), P-Block layer 7 (where P-Block layer 7 is formed from an AlGaN layer), p-type AlGaN contact layer 8a, metal layer 9 (where metal layer 9 is formed from a Ni layer), and reflection The electrode layer 10 (where the reflective electrode layer is formed of Au). The film thickness of the P-Block layer 7 is 44 nm to 48 nm. A reflective two-dimensional photonic crystal periodic structure 100 and a photonic crystal periodic structure are provided within a range of the thickness direction of the p-type AlGaN contact layer 8a and not exceeding the interface between the p-type AlGaN contact layer 8a and the P-Block layer 7. 100 has pores (column structure, pores) 101 (h). The pores 101 are provided at a distance G from the end surface in the direction of the sapphire substrate 1 to the interface between the multiple quantum well layer 5 and the i-guide layer 6 is 53 nm ～ At 61 nm, the distance G satisfies the Bragg reflection in the vertical direction.

The entire thickness of each layer formed by epitaxial growth can be measured using an optical interference film thickness measuring device. Furthermore, when the thickness of each layer is sufficiently different in the composition of adjacent layers (for example, when the Al composition ratio is different from 0.01 or more), the cross-section observation of the growth layer using a transmission electron microscope can be performed. To figure it out. When the thickness of each layer is thin, such as a multiple quantum well or a superlattice structure, TEM-EDS can be used to measure the thickness. The photonic crystal's periodic structure or shape and the distance between the quantum well layer and the photonic crystal can be measured by observing a HAADF (high-angle scattering annular dark field) image using a transmission electron microscope (STEM) mode. Figure it out.

FIG. 17 shows the relationship between the cumulative film thickness and the refractive index difference in the multilayer structure from the multiple quantum well layer 5 to the p-type AlGaN contact layer 8a related to the Bragg reflection in the vertical direction.

According to the formula of Bragg scattering conditions (mλ / n _1Deff = 2a, m: degree, n _1Deffav : effective refractive index of each film thickness of the multilayer structure from the end surface of the hole 101 (h) to the i-guide layer 6, λ : Design wavelength, a: period) to calculate the distance G (period) to obtain the effect of the Bragg reflection in the vertical direction and the film thickness of the P-Block layer 7.

The respective refractive indices (n) of the i-guide layer 6 and the P-Block layer 7 at the design wavelength of 275 nm are the i-guide layer 6 (n ₁ = 2.300) and the P-Block layer 7 (n ₂ = 2.594). The effective refractive index n _{1Deff is obtained} by the _formula of n _av = [n ₂ ² + (n ₁ ² −n ₂ ² ) (d / a) ² ] ^0.5 . When the film thickness of the i-guide layer 6 is set to d, for example, 1 nm, the value of d / a is 0.019, so n _{1Deff is} 2.589. If it is set to m = 1, and these are substituted into the above-mentioned expression of the Bragg scattering condition, the derivation period a is 53 nm. That is, the distance to obtain the reflection effect in the vertical direction is 53 nm here.

Table 5 shows the results of FDTD simulation analysis related to the Bragg reflection effect in the vertical direction.

[table 5]
[Note]
-G53 nm: set the monitor at a position 53 nm away from the interface between the quantum well layer 55 and the i-guide layer 6 in the direction of the sapphire substrate
+ G53 nm: Set the monitor at the position of 53 nm away from the interface between the quantum well layer 55 and the i-guide layer 6 in the direction of the p-type AlGaN contact layer: P-Block film thickness 44 nm / 40 nm

Table 5 shows the case where each of the P-Block layer film thicknesses of 40 nm and 44 nm is placed at a distance of 53 nm from the interface between the quantum well layer 55 and the i-guide layer 6 in the direction of the sapphire substrate 1 ( Table 5 "-G53 nm") and the case where it is placed at a distance of 53 nm in the direction of the p-type AlGaN contact layer 8a from the interface between the quantum well layer 55 and the i-guide layer 6 (Table 5 "+ G53 nm") The output ratio of each is compared with the output ratio of the film thickness of the P-Block layer to 44 nm and the film thickness of 40 nm.

According to Table 5, it can be confirmed that using each of the monitors above and below the quantum well layer, the output ratio of the 44 nm of the P-Block layer is about 2 times. In addition, the output value of the monitor (+ G53 nm) provided on the p-type AlGaN contact layer side of the P-Block layer with a film thickness of 40 nm was hardly reduced compared to the case of the p-type GaN contact layer. The reason is that the p-type AlGaN contact layer does not absorb as much as the p-type GaN contact layer.

From these results, it was confirmed that in the LED structure of the p-type AlGaN contact layer, the distance G to obtain the Bragg reflection effect in the vertical direction was also 53 nm.

Second, the reflective two-dimensional photonic crystal periodic structure 100 is shown in the xy plan view in FIG. 1B (b-2), and has a hole 101 (h) with a circle of radius R as a cross section. The layer 8a is formed of small air or the like, and is formed into a columnar structure (hole structure) in a triangular lattice shape at a period a along the x direction and the y direction. In addition, in order to prevent damage to the P-Block layer 7 caused by dry etching, the hole 101 (h) is a structure that does not reach the interface between the p-type AlGaN contact layer 8a and the P-Block layer 7, and is provided in the hole. A distance (G) between the end surface of the sapphire substrate 1 in the direction of 101 (h) and the quantum well layer 55 is in a range of 53 nm to 61 nm.

In the reflective two-dimensional photonic crystal periodic structure 100, deep-ultraviolet light TE light and TM light of a wavelength λ emitted by the multiple quantum well layer 5 are radiated in all directions and propagate through the medium in an elliptical polarization.

The reflective two-dimensional photonic crystal periodic structure 100 disposed in the p-type AlGaN contact layer 8a at a distance of G53 nm to 61 nm from the quantum well layer 55 is formed as a p-type AlGaN contact layer 8a having different refractive indices and air Two constructs. When the ratio R / a ratio of the radius R to the period a of the hole 101 (h) is set to, for example, 0.40, the filling factor f of the photonic crystal 100 is expressed by the formula f = 2π / 3 ^0.5 × (R / a) ² When calculated, f = 0.58. Furthermore, the effective refractive index n _2Deff is calculated from the refractive index n3 of the air n3 = 1.0, the refractive index n _{4 of the} p-type AlGaN contact layer 8, and the effective refractive index n _2Deff is calculated by the following formula: n _2Deff = (n ₄ ² + (n ₃ ² -n ₄ ² ) × f) ^0.5 = 1.921.

Furthermore, the wavelength range of deep ultraviolet (DUV) light is 200 nm to 355 nm, and the refractive index n and the extinction coefficient k are different depending on the wavelength. Therefore, if the selected wavelength λ changes, the calculation parameters of the above photonic crystal also change, so the film thickness of the P-Block layer and the distance between the quantum well layer and the two-dimensional photonic crystal will also change. In addition, the refractive index and extinction coefficient used in this calculation are literature values, but these values vary slightly according to their film thickness. Therefore, the film thickness of the above P-Block layer and The distance will also change.

Moreover, when the emission wavelength λ = 275 nm, the reflective two-dimensional photonic crystal periodic structure 100 satisfies the Bragg scattering condition (mλ / n _2Deff = 2a, where n _{2Deff is} the effective refractive index of the two-dimensional photonic crystal, a: 2D The photon band structure of TM light and TE light in the case of the period of PhC, m: the number of times) is obtained by the plane wave expansion method. 18 (a) and 18 (b) show respective photon band structure diagrams of TM light and TE light when R / a = 0.40.

In a two-dimensional reflective photonic crystal, as shown in FIG. 18 (a), TM light does not observe a photon band gap (PBG), but in TE light, as shown in FIG. 18 (b), it is in the first photon band (ω1TE). A larger PBG was observed with the second photon band (ω2TE). Moreover, the size of PBG in TE light is the largest at R / a = 0.40, and as R / a becomes larger, the PBG becomes larger.

However, as shown in the first embodiment of the present invention, as the film thickness of the P-Block layer 7 becomes thicker, the driving voltage (Vf) becomes higher. Therefore, to suppress Vf and make the film thickness of the P-Block layer as thin as possible, it is important that the light extraction efficiency (LEE) is greatly improved by the synergistic effect of vertical Bragg reflection and reflective two-dimensional photonic crystals. Optimize the film thickness of the P-Block layer. In this embodiment, a p-type contact layer is used in place of the p-type GaN contact layer in the first embodiment, and a p-type AlGaN contact that is transparent to the wavelength λ is obtained by simulation analysis using the FDTD method and the ray tracing method. In the deep UV LED structure of the layer, the synergistic effect between the vertical Bragg reflection and the reflective two-dimensional photonic crystal is obtained, and the LEE is significantly improved, and the appropriate conditions for the trade-off between the film thicknesses of the Vf and P-Block layers are also considered, that is, quantum The distance between the well layer 55 and the reflective two-dimensional photonic crystal structure, the thickness of the P-Block layer, and the parameters of the two-dimensional photonic crystal periodic structure (the number of times m and the cycle a and R that satisfy the Bragg scattering condition mλ / n _2Deff = 2a / a).

Table 6 shows the calculation model of the deep ultraviolet LED structure of the FDTD method, and Table 7 shows the parameters of the calculation model of the reflective two-dimensional photonic crystal structure.

[TABLE 6]

[TABLE 7]

FIG. 19 is a cross-sectional view near a photonic crystal periodic structure in a deep ultraviolet LED structure having a film thickness of 44 nm as an example of a calculation model of the FDTD method. In the construction of the calculation model, the film thickness of the P-Block layer is changed in the range of 4 nm in the range of 40 nm to 60 nm in 4 nm units. There are occasions when a non-reflective two-dimensional photonic crystal periodic structure (2D-PhC) is used. The comparison of the case of a reflective two-dimensional photonic crystal periodic structure (2D-PhC) is analyzed. The formation position of 2D-PhC is set from the interface between the P-Block layer and the p-type AlGaN contact layer to the interface between the metal layer (Ni) and the p-type AlGaN contact layer as shown in FIG. 19.

The simulation analysis results of the above calculation model are shown in FIG. 20 and FIG. 21. Fig. 20 shows the case where the P-Block layer is made variable in units of 4 nm in the range of film thickness of 40 nm to 60 nm, and 2D-PhC has no 2D-PhC when the number of times is m = 4 and R / a = 0.40. Changes in the respective output (w) of time and the case of 2D-PhC. As shown in FIG. 20, when there is no 2D-PhC and there is 2D-PhC, the film thickness of the P-Block layer is 44 nm to 52 nm and the output is greatly increased.

Also, according to FIG. 20, in the structure without 2D-PhC, the output of the P-Block layer when the film thickness is 44 nm to 52 nm is about twice as large as that when the film thickness is 40 nm. This phenomenon indicates that the laminated structure of the i-guide layer and the P-Block layer in the present structure can obtain a Bragg reflection effect in the vertical direction when the film thickness of the P-Block layer is 44 nm to 52 nm.

In addition, FIG. 21 is a graph showing the increase rate of LEE when a structure with 2D-PhC is compared with a structure without 2D-PhC under the same conditions. As shown in FIG. 21, it is shown that as the film thickness of the P-Block layer increases, the LEE increase rate also increases, and the P-Block film thickness has a correlation with the LEE increase rate. However, as described above, if the film thickness of the P-Block layer increases, Vf also increases. Therefore, the film thickness of the P-Block layer is preferably 44 nm, and is preferably selected to 48 nm.

The design of the reflective two-dimensional photonic crystal (2D-PhC) is in the 2D-PhC plane, according to the formula of Bragg scattering conditions mλ / n _2Deff = 2asinθ (where m: the number of times, n _2Deff : the 2D-PhC periodic structure Effective refractive index, λ: design wavelength, a: period of 2D-PhC). In the first embodiment, as shown in FIG. 7, the larger the R / a, the greater the change in the state density of the photons. Moreover, as shown in FIG. 8, DUV light incident on 2D-PhC formed near the quantum well layer (light emitting layer) generates a standing wave in the 2D-PhC plane. In addition, when the distance between the quantum well layer and the photonic crystal satisfies λ / 2n _1Deff , the DUV light incident on the 2D-PhC plane has a vertical Bragg reflection and is reflected toward the sapphire substrate.

It is considered that in the deep ultraviolet LED structure in this embodiment, when the distance between the quantum well layer and the 2D-PhC is 53 nm, the Bragg reflector is best satisfied in the vertical direction, so that a larger reflection effect can be obtained.

Based on these prerequisites, the optimal value of the distance (G) between the quantum well layer and the 2D-PhC that can obtain the synergistic effect of the Bragg reflection in the vertical direction and the 2D-PhC is obtained through simulation analysis.

The film thickness of the P-Block layer was set to 44 nm, and the output was confirmed depending on the difference in the distance G between the quantum well layer and 2D-PhC. Here, the distance G between the quantum well layer and the 2D-PhC is set to be variable in units of 4 nm between 1 nm and 61 nm. The 2D-PhC is set to R / a = 0.4, and the number of times is m = 4. The analysis results of the FDTD method are shown in FIG. 22.

As shown in FIG. 22, it was confirmed that the distance G between the quantum well layer and 2D-PhC was 53 nm, and the output was maximized.

In addition, FIG. 23 shows the increase rate of LEE under the same simulation conditions as in FIG. 22 in the case where there is a 2D-PhC structure without a 2D-PhC structure. The distance between the quantum well layer and 2D-PhC, G53 nm, also shows the largest increase in LEE, which is consistent with 53 nm, which is the distance that satisfies the above-mentioned Bragg condition in the vertical direction. That is, the period 53 nm, which indicates the maximum Bragg reflection effect in the vertical direction, satisfies the optimal conditions for obtaining the synergistic effect of the one-dimensional photonic crystal and the reflective two-dimensional photonic crystal in both the output and the increase magnification of LEE.

The distance between the quantum well layer and 2D-PhC is selected from 53 nm to 61 nm which exhibits a relatively large output.

Next, it was confirmed by FDTD method analysis to select the R / a and the number of times m for 2D-PhC. As the film thickness of the P-Block layer was 44 nm, a comparison was made between a structure without 2D-PhC and a structure with 2D-PhC. First, regarding the R / a dependency, the number of times is set to m = 4, and R / a = 0.20 to 0.40 is variable. Regarding the number of times dependency, R / a is set to R / a = 0.40, and is variable from m = 1 to 4. As a result of these, the comparison of the LEE increase magnification and the output value is shown in FIGS. 14 and 15.

FIG. 14 (a) shows the increase rate of LEE in each R / a at G53 nm when the number of times is m = 4, and R / a is R / a = 0.20, R / a = 0.30, and R / a = 0.40. Figure 14 (b) shows the R / a dependency of its output value. As shown in FIG. 14 (a), it can be confirmed that “pAlGaN_NiAu_Pblock44 nm_m4” is R / a = 0.20 and LEE is approximately doubled, but if R / a = 0.40, it is approximately 4 times. It can also be seen in FIG. 14 (b) that as R / a becomes larger, the output becomes larger.

Fig. 15 (a) shows the dependence of the number of times on the increase rate of LEE in each of the times when R / a = 0.40 is set at G53 nm, and the times are m = 1 to 4. Fig. 15 (b) also shows the output value. Number of dependencies. According to FIG. 15 (a), “pAlGaN_NiAu_Pblock44 nm_R / a0.40” is about 2 to 2.5 times the increase rate of LEE when the number of times m = 1 to 2, but about 4 times when the number of times m = 3 to 4. It can also be confirmed in FIG. 15 (b) that the number of times m = 3 to 4 is compared with the number of times m = 1 to 2 to obtain a larger output.

For such verification, the LEE value was obtained and confirmed by cross-simulation with the ray tracing method. Figure 24 shows the calculation model and analysis results of the ray tracing method. In the normal tracking method, since the nano-scale calculation cannot be performed, firstly, the present embodiment is calculated by cross simulation of multiplying the LEE value calculated by the ray tracing method with the LEE increase factor derived by the FDTD method. The LEE value of the LED structure. Table 8 shows the results.

[TABLE 8]

As shown in Table 8, when the film thickness of the P-Block layer is 44 nm, the distance between the quantum well layer and 2D-PhC is G53 nm, R / a = 0.40, and the number of times m = 3, the LEE is 63.5%. When m = 4, the LEE value is 62.2%. According to this embodiment, the LEE can be further improved.

(Third Embodiment)
As a deep ultraviolet LED according to the third embodiment of the present invention, the structure (cross-sectional view and top view) of an AlGaN deep ultraviolet LED with a design wavelength λ of 275 nm is shown in FIGS. 1C (c-1) and (c-2).

As shown in FIG. 1C, the LED structure of this embodiment uses the metal of the electrode portion of the deep ultraviolet LED structure of a p-type AlGaN contact layer transparent to the wavelength λ as the p-type contact layer in the second embodiment of the present invention. A modification example when the layer (Ni) and the reflective emitter electrode (Au) are replaced with an Rh electrode.

Compared with the Ni / Au electrode (reflection 20%), the Rh electrode (reflection 70%) has a higher reflectance. As shown in FIG. 20, the simulation results show that the Rh electrode has a higher output than the Ni / Au electrode. The reflection effect of 2D-PhC with R / a = 0.40 is approximately 100% in TE light, and it is inferior to this TM light. Polarized DUV light with a wavelength of 275 nm is calculated in the FDTD method simulation analysis shown in the present invention with a polarization degree of 0.35, and the intensity ratio is TE: TM = 7: 3. Therefore, it is considered that the reflection of TM light reaching the electrode through 2D-PhC in the Rh electrode is considered to have a higher output effect compared to the Ni / Au electrode.

The laminated structure body part of the LED structure in this embodiment is the same as the structure of the second embodiment, and only the electrodes are different. Therefore, the optimal condition for obtaining the synergistic effect of the Bragg reflection in the vertical direction and 2D-PhC is Under the same conditions as in the second embodiment, only the electrode was changed to Rh, and the FDTD method simulation analysis was performed. Table 9 shows the parameters of the calculation model of the deep ultraviolet LED structure of the FDTD method. The parameters of the calculation model of the reflective two-dimensional photonic crystal structure are shown in Table 7. The results of the FDTD method simulation analysis are shown in FIG. 22.

[TABLE 9]

In FIG. 22, the film thickness of the P-Block layer was set to 44 nm, and the output was confirmed depending on the difference (G) between the quantum well layer and 2D-PhC. Here, the distance G between the quantum well layer and 2D-PhC is set to be variable in units of 4 nm between 1 nm and 61 nm, 2D-PhC is set to R / a = 0.40, and the number of times m = 4.

As shown in FIG. 22, it can also be confirmed in the Rh electrode that the distance G between the quantum well layer and 2D-PhC is 53 nm and the output becomes the maximum.

In addition, FIG. 23 shows the increase rate of LEE under the same simulation conditions as in FIG. 22 when compared with the case where the structure has 2D-PhC without the structure with 2D-PhC. The distance between the quantum well layer and 2D-PhC, G53 nm, also shows the largest increase in LEE, which is consistent with 53 nm, which is the distance that satisfies the above-mentioned Bragg condition in the vertical direction. That is, the period 53 nm, which indicates the maximum reflection effect in the vertical direction, satisfies the optimal conditions for obtaining the synergistic effect of the one-dimensional photonic crystal and the reflective two-dimensional photonic crystal in both the output and the increase rate of LEE.

The distance between the quantum well layer and 2D-PhC is selected from 53 nm to 61 nm which exhibits a relatively large output.

Next, it was confirmed by FDTD method analysis to select the R / a and the number of times m for 2D-PhC. As the film thickness of the P-Block layer was 44 nm, a comparison was made between a structure without 2D-PhC and a structure with 2D-PhC. First, regarding the R / a dependency, the number of times is set to m = 4, and R / a = 0.20 to 0.40 is variable. Regarding the number of times dependency, R / a is set to R / a = 0.40, and is variable from m = 1 to 4. As a result of these, the comparison of the LEE increase magnification and the output value is shown in FIGS. 14 and 15.

FIG. 14 (a) shows the increase rate of LEE in each R / a at G53 nm when the number of times is m = 4, and R / a is R / a = 0.20, R / a = 0.30, and R / a = 0.40. Figure 14 (b) shows the R / a dependency of its output value. As shown in FIG. 14 (a), it can be confirmed that “pAlGaN_Rh_Pblock44 nm_m4” has R / a = 0.20 and LEE is approximately doubled. However, if R / a = 0.40, it is three times stronger. It can also be seen in FIG. 14 (b) that as R / a becomes larger, the output becomes larger.

Fig. 15 (a) shows the dependence of the number of times on the increase rate of LEE in each of the times when R / a = 0.40 is set at G53 nm, and the times are m = 1 to 4. Fig. 15 (b) also shows the output value. Number of dependencies. According to FIG. 15 (a), the “pAlGaN_Rh_Pblock44 nm_R / a0.40” is about 2 times the increase rate of LEE when the number of times m = 1 to 2, but about 3 times when the number of times m = 3 to 4. It can also be confirmed in FIG. 15 (b) that the number of times m = 3 to 4 is compared with the number of times m = 1 to 2 to obtain a larger output.

For such verification, the LEE value was obtained and confirmed by cross-simulation with the ray tracing method. Figure 25 shows the calculation model and analysis results of the ray tracing method. In the normal tracking method, since the nano-scale calculation cannot be performed, firstly, the present embodiment is calculated by cross simulation of multiplying the LEE value calculated by the ray tracing method with the LEE increase factor derived by the FDTD method. The LEE value of the LED structure. Table 10 shows the results.

[TABLE 10]

As shown in Table 10, the film thickness of the P-Block layer is 44 nm, the distance between the quantum well layer and 2D-PhC is G53 nm, R / a = 0.40, and the LEE is 58.7% when the number of times is m = 3, and when the number of times is m = 4 It shows a LEE value of 55.2%. According to this embodiment, the LEE can be further improved.

(Fourth Embodiment)
As a fourth embodiment of the present invention, a method for manufacturing a deep ultraviolet LED using a p-type GaN contact layer as a p-type contact layer will be described.

First, a sapphire substrate is used as a growth substrate, and an AlN template, a u-type AlGaN layer, an n-type AlGaN contact layer, and a multiple quantum well layer are sequentially laminated by crystal growth. Multiple quantum well layers are formed in the form of 3 layers of 2 nm wells and 7 nm of two barrier layers spaced between the well layers. An i-guide layer formed of AlN and a B-Block layer formed of a p-type AlGaN layer are formed thereon at 52 nm to 56 nm. A p-type GaN contact is laminated thereon. The entire thickness of each layer formed by epitaxial growth can be measured using an optical interference film thickness measuring device. Furthermore, when the thickness of each layer is sufficiently different in the composition of adjacent layers (for example, when the Al composition ratio is different from 0.01 or more), the cross-section observation of the growth layer using a transmission electron microscope can be performed. To figure it out. When the thickness of each layer is thin, such as a multiple quantum well or a superlattice structure, TEM-EDS can be used to measure the thickness.

Further, the deep ultraviolet LED laminated structure from the crystal growth to the p-type GaN contact layer forms a reflective two-dimensional photonic crystal periodic structure.

FIG. 26 is a diagram showing an example of a manufacturing process of a reflective two-dimensional photonic crystal periodic structure.

The processing of reflective two-dimensional photonic crystals uses nanoimprint lithography technology. The surface of the p-type GaN contact layer 208 has a warpage of 100 μm or more in the convex direction, so the resin mold 200 corresponds to the mold. In addition, in order to maintain the diameter of the hole approximately vertically and accurately during dry etching, a double-layer resist is used.

Specifically, in a wafer having a deep ultraviolet LED multilayer structure laminated to the p-type GaN contact layer 208, a lower resist 210 is spin-coated on the surface of the p-type GaN contact layer 208. Next, an upper layer resist 209 containing Si is spin-coated to form a double-layer resist (see FIG. 26 (a)).

For the upper resist, a resin mold 200 having a reverse pattern of a specific photonic crystal periodic structure is pressed to harden UV to transfer the photonic crystal pattern 211 to the upper resist 209 (see FIG. 26 (b)). . Next, the upper layer resist 209 is etched with an oxygen plasma to form a mask 212. Refer to FIG. 26 (c). Moreover, the mask 212 is etched by an ICP (inductively coupled plasma) plasma to a distance from the end face of the photonic crystal pattern (hole) 211 of the P-Block layer 207 to the quantum well layer 205 as 53 nm to 57 nm. Refer to FIG. 26 (d). The last remaining lower resist 210 is washed and cleaned. The photonic crystal's periodic structure or shape and the distance between the quantum well layer and the photonic crystal can be measured by observing a HAADF (high-angle scattering annular dark field) image using a transmission electron microscope (STEM) mode. Figure it out.

Furthermore, considering the damage to the p-type GaN contact layer caused by the etching, in order to repair it, an ammonium sulfide treatment or an annealing treatment may be performed.

Then, a metal layer (Ni) and a reflective electrode layer (Au) are formed on the reflective two-dimensional photon periodic structure. These metal layers (Ni) and reflective electrode layers (Au) can also be formed by a tilt evaporation method.

According to the oblique evaporation method, a metal layer (Ni) and a reflective electrode layer (Au) can be formed on the surface of a p-type GaN contact layer without embedding the metal layer (Ni) and the reflective electrode layer (Au) in the holes of the periodic structure of the reflective two-dimensional photonic crystal. Ni) and a reflective electrode layer (Au).

(Fifth Embodiment)
As a fifth embodiment of the present invention, a method for manufacturing a deep ultraviolet LED using a p-type AlGaN contact layer as a p-type contact layer will be described.

A sapphire substrate was used as a growth substrate, and an AlN template, a u-type AlGaN layer, an n-type AlGaN contact layer, and a multiple quantum well layer were sequentially laminated by crystal growth. Multiple quantum well layers are formed in the form of 3 layers of 2 nm wells and 7 nm of two barrier layers spaced between the well layers. An i-guide layer formed of AlN and a B-Block layer formed of a p-type AlGaN layer are formed thereon in a range of 44 nm to 48 nm. A p-type AlGaN contact layer is laminated thereon.

The entire thickness of each layer formed by epitaxial growth can be measured using an optical interference film thickness measuring device. Furthermore, when the thickness of each layer is sufficiently different in the composition of adjacent layers (for example, when the Al composition ratio is different from 0.01 or more), the cross-section observation of the growth layer using a transmission electron microscope To figure it out. When the thickness of each layer is thin, such as a multiple quantum well or a superlattice structure, TEM-EDS can be used to measure the thickness.

The deep ultraviolet LED multilayer structure formed by crystal growth to the p-type AlGaN contact layer forms a reflective two-dimensional photonic crystal periodic structure. The processing of the reflective two-dimensional photonic crystal is formed by the same method as that described in the fourth embodiment. (Refer to Figure 27).

That is, in a wafer having a deep ultraviolet LED multilayer structure laminated to the p-type AlGaN contact layer 208a, a lower resist 210 is spin-coated on the surface of the p-type AlGaN contact layer 208a. Next, a double-layer resist is formed by spin-coating the upper-layer resist 209 containing Si. The upper resist 209 is UV-cured by pressing a resin mold 200 having a reverse pattern of a specific photonic crystal periodic structure (see FIG. 27 (a)), and the photonic crystal pattern 211 is transferred to the upper resist. Agent 209 (see FIG. 27 (b)). Next, the upper layer resist 209 is etched with an oxygen plasma to form a mask 212. (Refer to FIG. 27 (c)). Then, the mask 212 is etched by an ICP plasma to a position within a distance of 53 nm to 61 nm from the end face of the photonic crystal pattern (hole) 211 of the P-Block layer 207 to the quantum well layer 205. (Refer to FIG. 27 (d)). Finally, the remaining lower resist 210 is washed and cleaned. The photonic crystal's periodic structure or shape and the distance between the quantum well layer and the photonic crystal can be measured by observing a HAADF (high-angle scattering annular dark field) image using a transmission electron microscope (STEM) mode. Figure it out.

Furthermore, considering the damage to the p-type GaN contact layer caused by the etching, in order to repair it, an ammonium sulfide treatment or an annealing treatment may be performed.

Then, a metal layer (Ni) and a reflective electrode layer (Au) are formed on the reflective two-dimensional photon periodic structure. These metal layers (Ni) and reflective electrode layers (Au) can also be formed by a tilt evaporation method.

According to the oblique evaporation method, a metal layer (Ni) and a reflective electrode layer (Au) can be formed on the surface of a p-type GaN contact layer without embedding the metal layer (Ni) and the reflective electrode layer (Au) in the holes of the periodic structure of the reflective two-dimensional photonic crystal. Ni) and a reflective electrode layer (Au).

In addition, in the electrode formation, after the reflective two-dimensional photonic crystal periodic structure is formed, an Rh electrode may be used instead of the metal layer (Ni) and the reflective electrode layer (Au). In addition, the Rh electrode may be formed by an oblique vapor deposition method.
[Industrial availability]

The invention can be applied to deep ultraviolet LEDs.

All publications, patents, and patent applications cited in this specification are directly incorporated into this specification by reference.

1‧‧‧ sapphire substrate

2‧‧‧AlN template

3‧‧‧u-type AlGaN layer

4‧‧‧n-type AlGaN contact layer

5‧‧‧ Multiple Quantum Well Formation

6‧‧‧i-guide layer

7‧‧‧P-Block layer

8‧‧‧p-type GaN contact layer

8a‧‧‧p-type AlGaN contact layer

9‧‧‧ metal layer (Ni)

10‧‧‧Reflective electrode layer (Au)

11‧‧‧Reflective electrode layer (Rh)

51, 53, 55‧‧‧‧ Quantum well formation

52, 54‧‧‧ Bund layer

100‧‧‧ reflective two-dimensional photonic crystal periodic structure

101 (h) ‧‧‧Hole (column structure, hole)

200‧‧‧ resin mold

205‧‧‧ Quantum Well Formation

206‧‧‧i-guide layer

207‧‧‧P-Block layer

208‧‧‧p-type GaN contact layer

208a‧‧‧p-type AlGaN contact layer

209‧‧‧ Upper resist

210‧‧‧ bottom resist

211‧‧‧photonic crystal pattern

212‧‧‧Mask

a‧‧‧cycle

R‧‧‧ radius of hole

1A (a-1) is a cross-sectional view showing an example of a structure of a deep ultraviolet LED according to the first embodiment of the present invention, and FIG. 1A (a-2) is a plan view showing a periodic two-dimensional photonic crystal structure.

FIG. 1B (b-1) is a cross-sectional view showing an example of a structure of a deep ultraviolet LED according to the second embodiment of the present invention, and FIG. 1B (b-2) is a plan view showing a periodic two-dimensional photonic crystal structure.

1C (c-1) is a cross-sectional view showing an example of a structure of a deep ultraviolet LED according to a third embodiment of the present invention, and FIG. 1C (c-2) is a plan view showing a periodic two-dimensional photonic crystal structure.

FIG. 2 shows the relationship between the cumulative film thickness and refractive index difference from multiple quantum well layers related to the vertical Bragg reflection.

FIG. 3A (a-1) is a photon band structure diagram of TM light in R / a = 0.40 of a plane wave expansion method of a two-dimensional photonic crystal, and FIG. 3A (a-2) is also a photon band structure diagram of TE light.

FIG. 3B (b-1) is a photon band structure diagram of TM light in R / a = 0.30 of a plane wave expansion method of a two-dimensional photonic crystal, and FIG. 3B (b-2) is also a photon band structure diagram of TE light.

FIG. 3C (c-1) is a photon band structure diagram of TM light in R / a = 0.20 of a plane wave expansion method of a two-dimensional photonic crystal, and FIG. 3C (c-2) is also a photon band structure diagram of TE light.

Fig. 4 is a cross-sectional view near a photonic crystal in a p-Block layer with a film thickness of 40 nm in a calculation model of the FDTD method.

FIG. 5 is a diagram showing the analysis results of the FDTD method related to the comparison of the output values of the two-dimensional photonic crystal with and without.

FIG. 6 is a diagram showing the analysis results of the FDTD method related to the comparison of the increase magnification of LEE with and without the two-dimensional photonic crystal.

FIG. 7 is a graph showing the state density of photons in a two-dimensional photonic crystal.

FIG. 8 is a diagram showing the principle of high reflection of a reflective two-dimensional photonic crystal structure that meets the Bragg reflection conditions in the vertical direction.

9 (a)-(d) are graphs showing the change with time of the electric field intensity from the quantum well layer to the vicinity of the p-type GaN contact layer.

FIG. 10 is a diagram showing the analysis results of the FDTD method related to the comparison of the film thickness of the P-Block layer in the p-type GaN contact layer and the comparison of the output value that makes the distance between the quantum well layer and the two-dimensional photonic crystal variable.

FIG. 11 is a diagram showing the analysis results of the FDTD method related to the comparison of the film thickness of the P-Block layer in the p-type GaN contact layer and the comparison of the increase rate of the LEE with a variable distance between the quantum well layer and the two-dimensional photonic crystal.

Fig. 12 (a) shows the R / a dependence of the LEE increase magnifications when the film thickness of the P-Block layer is 52 nm and 56 nm. Fig. 12 (b) also shows the R / a dependence of each output value. Illustration.

FIG. 13 (a) is a graph showing the number-dependent dependence of each LEE increase factor when the film thickness of the P-Block layer is 52 nm and 56 nm, and FIG. 13 (b) is a graph showing the number-dependent dependence of each output value.

FIG. 14 (a) is an R / showing the increase rate of LEE at a p-type GaN contact layer / P-Block layer with a film thickness of 53 nm and a p-type AlGaN contact layer / P-Block layer with a film thickness of 44 nm and an order of m = 4. a dependency, FIG. 14 (b) is a graph also showing the R / a dependency of the output value.

Fig. 15 (a) shows the number of times of increase in LEE when the p-type GaN contact layer / P-Block layer has a film thickness of 53 nm and the p-type AlGaN contact layer / P-Block layer has a film thickness of 44 nm and R / a = 0.40. Dependency FIG. 15 (b) is a graph showing the dependency of the number of times on the output value.

16 is a diagram showing a LEE analysis model of a ray tracing method in the structure of a p-type GaN contact layer.

FIG. 17 is a graph showing the relationship between the cumulative film thickness and refractive index difference from multiple quantum well layers in relation to the Bragg reflection in the vertical direction.

Fig. 18 (a) is a photon band structure diagram of TM light in R / a = 0.40 of a plane wave expansion method of a two-dimensional photonic crystal, and Fig. 18 (b) is a photon band structure diagram of TE light as well.

FIG. 19 is a cross-sectional view near a photonic crystal in a p-Block layer with a film thickness of 44 nm calculated by the FDTD method.

FIG. 20 is a diagram showing the analysis results of the FDTD method related to the comparison of the presence and absence of two-dimensional photonic crystal output values.

FIG. 21 is a diagram showing the analysis results of the FDTD method related to the comparison of the increase magnification of LEE with and without the two-dimensional photonic crystal.

FIG. 22 is a diagram showing an analysis result of the FDTD method in a p-type AlGaN contact layer, which is related to a comparison of an output value in which a distance between a quantum well layer and a two-dimensional photonic crystal is variable.

FIG. 23 is a diagram showing the analysis results of the FDTD method in the p-type AlGaN contact layer, which is related to the comparison of the LEE increase magnification that makes the distance between the quantum well layer and the two-dimensional photonic crystal variable.

FIG. 24 is a diagram showing a LEE analysis model of a ray tracing method when an electrode is a NiAu electrode in a structure of a p-type AlGaN contact layer.

25 is a diagram showing a LEE analysis model of a ray tracing method when an electrode is a Rh electrode in the structure of a p-type AlGaN contact layer.

26 (a) to (d) are diagrams showing an example of a manufacturing process of a reflective two-dimensional photonic crystal periodic structure in a deep ultraviolet LED structure using a p-type GaN contact layer.

27 (a) to (d) are diagrams showing an example of a manufacturing process of a reflective two-dimensional photonic crystal periodic structure in a deep ultraviolet LED structure using a p-type AlGaN contact layer.

Claims (6)

A deep ultraviolet LED is characterized in that it is a design wavelength set to λ, and has a reflective electrode layer (Au), a metal layer (Ni), a p-type GaN contact layer, and A P-Block layer formed of an AlGaN layer, an i-guide layer formed of an AlN layer, a multiple quantum well layer, an n-type AlGaN contact layer, a u-type AlGaN layer, an AlN template, and the above sapphire substrate, and the above-mentioned P-Block layer The film thickness is 52 nm to 56 nm, and it is provided in a range from the interface of the metal layer and the p-type GaN contact layer in the thickness direction of the p-type GaN contact layer and does not exceed the p-type GaN contact layer and the above. The reflective two-dimensional photonic crystal periodic structure with a plurality of holes is located at the interface of the P-Block layer. The holes are from the end surface of the sapphire substrate in the direction of the holes to the multiple quantum well layer and the i-guide. The distance up to the interface of the layer satisfies λ / 2n _1Dneff in the vertical direction. The distance ranges from 53 nm to 57 nm. The above-mentioned reflective two-dimensional photonic crystal periodic structure has a photon band gap opened with respect to the TE polarized component. Two-dimensional photonic crystal The period a of the phase structure satisfies the Bragg condition with respect to the light of the design wavelength λ described above, and is in Bragg's conditional expression mλ / n _2Deff = 2a (where m: the number of times, λ: the design wavelength, and n _2Deff : the two-dimensional photonic crystal The effective index of refraction, a: the period of the two-dimensional photonic crystal) m satisfies 2 ≦ m ≦ 4, and when the radius of the above-mentioned hole is set to R, the R / a ratio satisfies 0.30 ≦ R / a ≦ 0.40. A deep ultraviolet LED is characterized in that it is a design wavelength set to λ, and has a reflective electrode layer (Au), a metal layer (Ni), and a p-type transparent to the wavelength λ in order from the opposite side from the sapphire substrate. AlGaN contact layer, P-Block layer formed from p-type AlGaN layer, i-guide layer formed from AlN layer, multiple quantum well layer, n-type AlGaN contact layer, u-type AlGaN layer, AlN template, and the above sapphire substrate, The P-Block layer has a film thickness of 44 nm to 48 nm and is provided in a range from the interface of the metal layer and the p-type AlGaN contact layer in a thickness direction of the p-type AlGaN contact layer and does not exceed the p A reflective two-dimensional photonic crystal periodic structure with a plurality of holes at the interface of the Al-type AlGaN contact layer and the P-Block layer, the holes are from the end surface of the sapphire substrate in the direction of the holes to the multiple quantum wells The distance from the interface between the layer and the i-guide layer satisfies λ / 2n _1Dneff in the vertical direction. The distance ranges from 53 nm to 61 nm. The above-mentioned reflective two-dimensional photonic crystal periodic structure has photons that are open relative to the TE polarized component. Bandgap, Said period of reflection type two-dimensional photonic crystal periodic structure with respect to light having a design wavelength of [lambda] satisfying the Bragg condition, and in Prague conditional equation _mλ / n 2Deff = 2a (wherein, m: number of times, λ: design wavelength, n- _2Deff : effective refractive index of a two-dimensional photonic crystal, a: the number of times of a two-dimensional photonic crystal) m satisfies 1 ≦ m ≦ 4, and when the radius of the above-mentioned hole is set to R, the R / a ratio satisfies 0.20 ≦ R /a≦0.40. A deep ultraviolet LED is characterized in that it is a design wavelength set to λ, and has a reflective electrode layer (Rh) in order from the opposite side to the sapphire substrate, a p-type AlGaN contact layer transparent to the wavelength λ, and p A P-Block layer formed of an AlGaN layer, an i-guide layer formed of an AlN layer, a multiple quantum well layer, an n-type AlGaN contact layer, a u-type AlGaN layer, an AlN template, and the above sapphire substrate, and the above-mentioned P-Block layer The film thickness is 44 nm to 48 nm, and it is provided in a range from the interface between the reflective electrode layer and the p-type AlGaN contact layer in the thickness direction of the p-type AlGaN contact layer and does not exceed the p-type AlGaN contact layer and The position of the interface of the P-Block layer is a reflective two-dimensional photonic crystal periodic structure with a plurality of voids. The voids are from the end surface of the sapphire substrate in the direction of the voids to the multiple quantum well layer and the i- The distance up to the interface of the guide layer satisfies λ / 2n _1Dneff in the vertical direction. The distance ranges from 53 nm to 61 nm. The above-mentioned reflective two-dimensional photonic crystal periodic structure has a photon band gap opened with respect to the TE polarized component. The period a of the periodic structure of the reflective two-dimensional photonic crystal satisfies the condition of Bragg with respect to the light of the design wavelength λ described above, and is in Bragg's conditional expression mλ / n _2Deff = 2a (where m: the number of times, λ: the design wavelength, n _2Deff : The effective refractive index of the two-dimensional photonic crystal, a: the number of times of the two-dimensional photonic crystal) m satisfies 1 ≦ m ≦ 4, and when the radius of the above-mentioned hole is set to R, the R / a ratio satisfies 0.20 ≦ R / a ≦ 0.40. A manufacturing method of deep ultraviolet LED, which is a manufacturing method of deep ultraviolet LED with design wavelength set to λ, and has the following steps: A step of preparing a laminated structure in which a sapphire substrate is used as a growth substrate, wherein a reflective electrode layer, a metal layer, a p-type GaN contact layer, and a p-type transparent layer with respect to the wavelength λ are formed in this order from the side opposite to the sapphire substrate. In the step of forming a P-Block layer formed of a type AlGaN layer, an i-guide layer formed of an AlN layer, a multiple quantum well layer, an n-type AlGaN contact layer, a u-type AlGaN layer, and an AlN template, the P -The film thickness of the Block layer is 52 nm ～ 56 nm for crystal growth; Formed at a position provided in a range from the interface of the metal layer and the p-type GaN contact layer in a thickness direction of the p-type GaN contact layer and not exceeding the interface of the p-type GaN contact layer and the P-Block layer. The step of periodically constructing a reflective two-dimensional photonic crystal having a plurality of holes, the holes are formed from the end surface of the sapphire substrate in the direction of the holes to the interface between the multiple quantum well layer and the i-guide layer. Steps with a distance of 53 nm to 57 nm; A step of preparing a mold for forming the reflective two-dimensional photonic crystal periodic structure, and a step of forming a resist layer on the p-type GaN contact layer and transferring the structure of the mold by a nano-imprint method; A step of etching the p-type GaN contact layer by using the resist layer as a mask to form a two-dimensional photonic crystal periodic structure; A step of forming the above-mentioned reflective two-dimensional photonic crystal structure, and forming the above-mentioned metal layer by oblique evaporation in this order; and A step of forming a reflective electrode layer on the metal layer. A manufacturing method of deep ultraviolet LED, which is a manufacturing method of deep ultraviolet LED with design wavelength set to λ, and has the following steps: A step of forming a laminated structure in which a sapphire substrate is used as a growth substrate, wherein a p-type AlGaN contact layer containing a reflective electrode layer, a metal layer, a transparent layer with respect to a wavelength λ, and the In the step of forming a P-Block layer formed of a type AlGaN layer, an i-guide layer formed of an AlN layer, a multiple quantum well layer, an n-type AlGaN contact layer, a u-type AlGaN layer, and an AlN template, the P -The film thickness of the Block layer is 44 nm ～ 48 nm for crystal growth; Forming a position provided in a range from the interface between the metal layer and the p-type AlGaN contact layer in a thickness direction of the p-type AlGaN contact layer and not exceeding the interface between the p-type AlGaN contact layer and the P-Block layer A step of a periodic structure of a reflective two-dimensional photonic crystal having a plurality of voids, the voids being formed at a distance from an end face of the growth substrate in the direction of the voids to an interface between the multiple quantum well layer and the i-guide layer Steps for positions from 53 nm to 61 nm; A step of preparing a mold for forming the reflective two-dimensional photonic crystal periodic structure, and a step of forming a resist layer on the p-type AlGaN contact layer and transferring the structure of the mold by a nano-imprint method; A step of etching the p-type AlGaN contact layer using the resist layer as a mask to form a two-dimensional photonic crystal periodic structure; Forming the reflective two-dimensional photonic crystal structure, and forming the metal layer by a tilt evaporation method; and A step of forming a reflective electrode layer on the metal layer. A manufacturing method of deep ultraviolet LED, which is a manufacturing method of deep ultraviolet LED with design wavelength set to λ, and has the following steps: A step of forming a laminated structure in which a sapphire substrate is used as a growth substrate, wherein a p-type AlGaN contact layer including a reflective electrode layer, which is transparent to the wavelength λ, and a p-type AlGaN layer are formed in order from the opposite side to the sapphire substrate. In the step of forming a P-Block layer, an i-guide layer formed by an AlN layer, a multiple quantum well layer, an n-type AlGaN contact layer, a u-type AlGaN layer, and an AlN template, the above-mentioned P-Block layer is formed. The film thickness is 44 nm ～ 48 nm for crystal growth; Forming a position provided in a range from the interface between the metal layer and the p-type AlGaN contact layer in a thickness direction of the p-type AlGaN contact layer and not exceeding the interface between the p-type AlGaN contact layer and the P-Block layer Steps of periodic structure of a reflective two-dimensional photonic crystal with a plurality of holes; A step of forming the void at a position ranging from 53 nm to 61 nm from an end surface of the growth substrate in the direction of the void to an interface between the multiple quantum well layer and the i-guide layer; A step of preparing a mold for forming the reflective two-dimensional photonic crystal periodic structure, and a step of forming a resist layer on the p-type AlGaN contact layer and transferring the structure of the mold by a nano-imprint method; A step of etching the p-type AlGaN contact layer using the resist layer as a mask to form a two-dimensional photonic crystal periodic structure; and Forming the reflective two-dimensional photonic crystal structure, and forming the reflective electrode layer by an oblique vapor deposition method.